Today's Message Index:
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1. 05:41 AM - Re: Need 1,2 & 3 amp fuses (Charlie England)
2. 06:08 AM - Alternator capacity (tomcostanza)
Message 1
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| Subject: | Re: Need 1,2 & 3 amp fuses |
Robert L. Nuckolls, III wrote:
> <nuckolls.bob@cox.net>
>
> At 08:08 PM 11/7/2008 +0000, you wrote:
>
>> Bill
>>
>>
>>
>> I am not an EE, as a matter of fact I m a Civil Eng, but it seems to
>> me that although fuses are designed to protect the wire, the current
>> (which determines the fuse Amp) that runs through the wire depends on
>> the device it serves.
>>
>> For example, when installing the GPSx96 in the panel the instructions
>> call for a 1A fuse or CB, and the AOA Cpu from Proprietary (now AFS)
>> calls for 4A, and Flightcom 403 intercom call for AWG 20 or 22 wire
>> and 1A breaker/fuse.
>>
>>
>>
>> Am I missing something?
>
> It's a matter of perspective. Folks who sell you an
> electro-whizzy would appreciate it if you did not
> power their 100 milliampere device with a 14AWG
> wire and 15A breaker. The flight safety guys wouldn't
> care, their job is to see that faults on the feeder
> don't unnecessarily increase risk to the airframe.
>
> But if the electro-whizzy shorts a 15-cent capacitor
> and burns a trace on a board, the repairs may be
> costly if not impossible. As a practical matter, you
> (as system integrator, owner and operator) can choose
> to run 14AWG wire for very low voltage drop and protect
> with a 1A fuse for ECB protection without insulting
> the bureaucrat or warranty service manager's sensibilities.
> In the final analysis, you're the one who does the
> implementation and is required to shoulder consequences.
>
> This is one feature of Greg Richter's one-size-fits-all
> philosophy of populating the power distribution with
> one value of protection and routing power all over the
> airplane on one size of wire. While it relieves the
> installer of having to make any decisions it
> keeps the thoughtful builder from tailoring system
> components to satisfy a variety of design goals.
>
> Bob . . .
It seems worth mentioning that in the situations mentioned & others like
them, the manufacturer is saving himself the expense of building
protection into his device and shifting responsibility for protection to
the installer. Now, if something burns, he can blame *you* instead of
accepting responsibility for his design.
Charlie
Message 2
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| Subject: | Alternator capacity |
Hi all,
What should I consider when I calculate the capacity of an alternator? I've read
Bob's posts about never seeing a situation that couldn't be served by a 40A
unit. But if I just add the requirements of each item, I get closer to 60A.
Should I consider things like landing/taxi lights (I have 4 bulbs @ 6.5A each),
or count them as zero (since they will only be used for a few minutes before,
during, and after landing)? What else am I missing?
Thanks.
--------
Clear Skies,
Tom Costanza
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=213014#213014
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